Such a method and system are used in particular in the field of plant automation, wherein a number of automation systems are generally used to control a plant. One important sub-aspect here is the use of variables of one automation system in another automation system. The variables, which are used by other communication partners, have to be made available by the system holding the originals of the variables.
Fundamentally different methods are currently used for—read or even write—access from one automation system to a variable of another automation system. Special access functions, for example the function modules according to IEC 61131-5 or the system functions “GET/PUT” of the SIMATIC S7, are therefore used. These access functions differentiate based on reading and writing the variables and require the configuration of a connection between the two automation systems, which then, has to be indicated at the access functions, or at least the identification of the automation system containing the variables. Also the name or address of the variables must be specified to the access functions and a local variable must be established and indicated at the access function, which is to assume the value of the variable. By calling up the access function the variable thus identified is read or written and the value is made available to the program or taken over by it.
Alternatively a table-based method for the exchange of variable values is for example integrated in the SIMATIC S7 system. To this end the automation systems, which wish to exchange variable values, are inserted into the table as columns. The identification—name or address—of the variables, which are to have the same value, is then input in the respective rows. One cell of each row of the table is identified as a transmit variable, in other words the value of said variable is transmitted to the other variables shown in the same row.
These existing methods are characterized in that from a user's point of view additional methods have to be used for access to variable values of another automation system, compared with access to local variables.